Buggy code:
public static final Object CONTINUE_TRAVERSAL_BUT_DONT_GO_DEEPER = new Object ( ) ; public static final Object STOP_TRAVERSAL = new Object ( ) ; public Object component ( Component component ) { } } private final class RemovedBehaviorChange extends Change { private static final long serialVersionUID = 1L ; private final IBehavior behavior ; public RemovedBehaviorChange ( IBehavior behavior ) { } public void undo ( ) { } public String toString ( ) { } } private final class AddedBehaviorChange extends Change { private static final long serialVersionUID = 1L ; private final IBehavior behavior ; public AddedBehaviorChange ( IBehavior behavior ) { } public void undo ( ) { } public String toString ( ) { } } protected static final class EnabledChange extends Change { private static final long serialVersionUID = 1L ; private final Component component ; private final boolean enabled ; EnabledChange ( final Component component ) { } public String toString ( ) { } public void undo ( ) { } } protected static final class VisibilityChange extends Change { private static final long serialVersionUID = 1L ; private final Component component ; private final boolean visible ; VisibilityChange ( final Component component ) { } public String toString ( ) { } public void undo ( ) { } } public static final Action ENABLE = new Action ( Action . ENABLE ) ; public static final char PATH_SEPARATOR = ':' ; public static final Action RENDER = new Action ( Action . RENDER ) ; private static final int FLAG_AUTO = 1 ; private static final int FLAG_ESCAPE_MODEL_STRINGS = 2 ; private static final int FLAG_INHERITABLE_MODEL = 4 ; private static final int FLAG_VERSIONED = 8 ; private static final int FLAG_VISIBLE = 16 ; private static final int FLAG_RENDER_BODY_ONLY = 32 ; private static final int FLAG_IGNORE_ATTRIBUTE_MODIFIER = 64 ; private static final int FLAG_ENABLED = 128 ; private static final int FLAG_IS_RENDERED_ONCE = 4096 ; private static final int FLAG_IS_RENDER_ALLOWED = 8192 ; private static final int FLAG_OUTPUT_MARKUP_ID = 16384 ; private static final int FLAG_PLACEHOLDER = 32768 ; protected static final int FLAG_RESERVED1 = 256 ; protected static final int FLAG_RESERVED2 = 512 ; protected static final int FLAG_RESERVED3 = 1024 ; protected static final int FLAG_RESERVED4 = 2048 ; protected static final int FLAG_RESERVED5 = 65536 ; protected static final int FLAG_RESERVED6 = 131072 ; protected static final int FLAG_RESERVED7 = 262144 ; protected static final int FLAG_RESERVED8 = 524288 ; private static final int FLAG_ATTACHED = 536870912 ; private static final int FLAG_ATTACHING = 1073741824 ; private static final int FLAG_DETACHING = - 2147483648 ; private static final MetaDataKey BORDER_KEY = new MetaDataKey ( IComponentBorder . class ) { private static final long serialVersionUID = 1L ; } ; private static final IModelComparator defaultModelComparator = new IModelComparator ( ) { private static final long serialVersionUID = 1L ; public boolean compare ( Component component , Object b ) { } } ; private static final Logger log = LoggerFactory . getLogger ( Component . class ) ; private static final String MARKUP_ID_ATTR_NAME = "id" ; private static final long serialVersionUID = 1L ; private ArrayList behaviors = null ; private int flags = ( ( ( ( Component . FLAG_VISIBLE ) | ( Component . FLAG_ESCAPE_MODEL_STRINGS ) ) | ( Component . FLAG_VERSIONED ) ) | ( Component . FLAG_ENABLED ) ) | ( Component . FLAG_IS_RENDER_ALLOWED ) ; private String id ; private MetaDataEntry [ ] metaData ; IModel model ; private MarkupContainer parent ; int markupIndex = - 1 ; public Component ( final String id ) { } public Component ( final String id , final IModel model ) { } public Component add ( final IBehavior behavior ) { } public Component remove ( final IBehavior behavior ) { if ( behavior == null ) { throw new IllegalArgumentException ( "Argument<seq2seq4repair_space>`behavior`<seq2seq4repair_space>cannot<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; } <START_BUG> if ( ( ( behaviors ) == null ) || ( ( ! ( behaviors . contains ( behavior ) ) ) == false ) ) { <END_BUG> throw new IllegalStateException ( ( "Tried<seq2seq4repair_space>to<seq2seq4repair_space>remove<seq2seq4repair_space>a<seq2seq4repair_space>behavior<seq2seq4repair_space>that<seq2seq4repair_space>was<seq2seq4repair_space>not<seq2seq4repair_space>added<seq2seq4repair_space>to<seq2seq4repair_space>the<seq2seq4repair_space>component.<seq2seq4repair_space>Behavior:<seq2seq4repair_space>" + ( behavior . toString ( ) ) ) ) ; } if ( ! ( behavior . isTemporary ( ) ) ) { addStateChange ( new Component . RemovedBehaviorChange ( behavior ) ) ; } behaviors . remove ( behavior ) ; return this ; } public final boolean continueToOriginalDestination ( ) { } public final void debug ( final String message ) { } public void detachModels ( ) { } public final void error ( final Serializable message ) { } public final void fatal ( final String message ) { } public final MarkupContainer findParent ( final Class c ) { } public final MarkupContainer findParentWithAssociatedMarkup ( ) { } public final Application getApplication ( ) { } public final List getBehaviors ( ) { } public final String getClassRelativePath ( ) { } public final IConverter getConverter ( ) { } public IConverter getConverter ( Class type ) { } public final boolean getEscapeModelStrings ( ) { } public final FeedbackMessage getFeedbackMessage ( ) { } public String getId ( ) { } public Locale getLocale ( ) { } public final Localizer getLocalizer ( ) { } public final ValueMap getMarkupAttributes ( ) { } public String getMarkupId ( ) { } final boolean hasMarkupIdMetaData ( ) { } final void setMarkupIdMetaData ( String markupId ) { } public final Serializable getMetaData ( final MetaDataKey key ) { } public final IModel getModel ( ) { } public final Object getModelObject ( ) { } public final String getModelObjectAsString ( ) { } public final Page getPage ( ) { } public final IPageFactory getPageFactory ( ) { } public final String getPageRelativePath ( ) { } public final MarkupContainer getParent ( ) { } public final String getPath ( ) { } public final boolean getRenderBodyOnly ( ) { } public final Request getRequest ( ) { }

Fix:
if ( ( ( behaviors ) == null ) || ( ! ( behaviors . contains ( behavior ) ) ) ) {